Polyurethanes and other types of elastomers and foams are used extensively in many kinds of safety padding, such as knee protectors for contact sports such as wrestling, protective knee, shoulder and arm pads for football and soccer players, ice hockey and basketball players, and the like. Conventional polyurethane foams and elastomers currently in use for these applications are intended to perform the functions of load distribution and energy attenuation or absorption. Experimental and practical evidence shows that although such foams and elastomers are good load distributors, they are frequently deficient in their shock and energy-attenuating capabilities. Ball rebound and pendulum impact test data for many of these foams and elastomers reveal that they possess fairly high rebound velocity due to their relatively low hysteresis. Moreover, they exhibit high-peak deceleration and severity index. Neither of these properties are conducive to their functioning as good energy attenuating polymeric substances.
In the field of footwear, insoles, outsoles, and other footwear components exhibiting energy-moderating or attenuating properties have been known for some time. Semi-flexible urethane foams have been used extensively in automotive interior safety padding such as crash pads, sun visors, arm rests, door panels, steering wheel panels, and the like. Stiffer semi-flexible foams and elastomers have been used in exterior safety applications in particular, as shock-attenuating bumpers.
However, most of the products utilized by the automotive and footwear manufacturers exhibit relatively low hysteresis which is detrimental to good energy-attenuation. Other approaches have taken the form of a combination of a polyurethane exterior deformable front-pad backed by a relatively complicated hydraulic shock absorption system as, for example, represented by the new automotive bumpers. Such approaches are not desirable from an economic point of view.
Attempts have been made to modify polyurethane foams and elastomers to obtain materials which possess more efficient energy-attenuating properties. For example, semi-flexible shock absorbing polyurethane foams prepared from a polyether triol, a compound having a single reactive hydrogen, an aromatic polyisocyanate, blowing agent, chain extender and a catalyst have been made. While these materials exhibit good shock-absorbing properties, the single reactive hydrogen reactant which is a naphthol, naphtholamine or a hydroabietyl alcohol imparts the undesirable characteristic odor of these aromatic compounds to the resulting foam. Accordingly, this approach to shock-absorbing polyurethanes is not particularly desirable.
Additionally, tire filling compounds have been formed from polyether polyols having equivalent weights from 900 to 1800, and polyisocyanates at isocyanate indexes of 0.8 to 2.0. The resulting polyurethanes exhibit very high rebound resiliency and are not suitable as energy-moderating polymers.
Thus, what is needed is polymeric compound having both viscoelastic and shock-attenuation properties.